Articles of footwear generally include two primary elements: an upper and a sole structure. The upper is often formed from a plurality of material elements (e.g., textiles, polymer sheet layers, foam layers, leather, synthetic leather) that are stitched or adhesively bonded together to form a void in the interior of the footwear for comfortably and securely receiving a foot. More particularly, the upper forms a structure that extends over instep and toe areas of the foot, along medial and lateral sides of the foot, and around a heel area of the foot. The upper may also incorporate a lacing system to adjust fit of the footwear, as well as permitting entry and removal of the foot from the void within the upper. In addition, the upper may include a tongue that extends under the lacing system to enhance adjustability and comfort of the footwear, and the upper may incorporate a heel counter.
The various material elements forming the upper impart different properties to different areas of the upper. For example, textile elements may provide breathability and may absorb moisture from the foot, foam layers may compress to impart comfort, and leather may impart durability and wear-resistance. As the number of material elements increases, the overall mass of the footwear may increase proportionally. One of the challenges with designing athletic footwear is to provide a designer with freedom of design to combine various materials for an upper to achieve a desired appearance while minimizing the weight of the upper. Although numerous materials could be combined and used to provide a desired design, the design could result in a heavier upper, which may diminish mobility, performance, and comfort for a wearer.
The time and expense associated with transporting, stocking, cutting, and joining material elements may also increase as the number of material elements of an upper increases. Additionally, waste material from cutting and stitching processes may accumulate to a greater degree as the number of material elements incorporated into an upper increases. Moreover, products with a greater number of material elements may be more difficult to recycle than products formed from fewer material elements. By decreasing the number of material elements, therefore, the mass of the footwear and waste may be decreased, while increasing manufacturing efficiency and recyclability.
In view of these considerations, there is a need for an article of footwear that advantageously includes a strong, lightweight structure that also provides a designer with a substantial degree of design freedom when creating an article of footwear with a stylish design.